Tracking Animal-Dispersed Seedlings Using 15N Xylem Injection Method

Abstract

Although various seed-marking methods have been developed for seed dispersal, it remains difficult to track the actual patterns of seed dispersal and seedling recruitment. Thus, new labeling methods that accurately track seedling establishment along with seed movement would help us better understand seed dispersal. Here, we developed a new nondestructive method using 15N xylem injection to track seed dispersal and seedling recruitment based on the enriched isotopic signals in the mature seeds. Our results first showed that xylem injection of 15N successfully enriched 15N both in the acorns and seedlings of Quercus variabilis. By marking acorns and seedlings with 15N stable isotopes, we successfully tracked seedlings established from acorns dispersed by seed-eating animals in the field. Our xylem 15N injection caused little alteration to seeds and showed no significant effects on seed selection by seed-eating animals as well as seed germination and seedling establishment, verifying the validity of the 15N xylem injection method to track seedling establishment. Our xylem 15N injection method is expected to be a powerful tool for tracking seed dispersal and seedling recruitment mediated by seed-eating animals in seed dispersal ecology.

A new technique for stain-marking of seeds with safranine to track seed dispersal and seed bank dynamics

“…Several methods have been developed for the study of seed dispersal; these include the surgical implantation of magnets ( Alverson and Díaz, 1989 ), attachment of colored threads or tags to seeds ( Forget, 1992 ; Hirsch et al, 2012a ; Deng et al, 2020 ), radioisotope labeling ( Vander Wall, 1994 ), fluorescent microsphere and dye powder labeling ( Levey and Sargent, 2000 ), stable isotope ( 15 N) analysis ( Carlo et al, 2009 ; Wang et al, 2021 ), attachment passive integrated transponders (PITs) tags ( Suselbeek et al, 2013 ); and molecular or genetic marking ( Ouborg et al, 1999 ; Godoy and Jordano, 2001 ; Grivet et al, 2005 ; Hardesty et al, 2006 ). These methods can help researchers to match dispersed seeds and seedlings with their parent plants in some situations; however, most are prohibitively expensive, logistically intractable, or excessively laborious and time consuming.…”